1. Field of Invention
This invention relates to an inductively coupled plasma chemical vapor deposition(ICP CVD) technology, and more particularly, to amorphous silicon, micro crystalline silicon, thin film silicon nitride and thin film amorphous silicon transistors fabricated by the utilization thereof.
2. Related Art
Generally, thin amorphous silicon, micro crystalline silicon and amorphous silicon film have been widely used in semiconductor and liquid crystal devices. In addition, thin amorphous silicon film transistors (a-Si TFT) have been widely used as driving elements of pixel electrodes in liquid crystal displays. In particular, a hydrogenized amorphous silicon transistor(a-Si:H TFT) is widely used for its superiority in the areas of yield and utilization in large area display devices.
Plasma enhanced chemical vapor deposition(PECVD) is currently used to manufacture thin amorphous silicon film, thin micro crystalline silicon film, thin silicon nitride film and thin amorphous silicon film transistors. But this type of vapor deposition due to its low plasma density of 10.sup.10 cm.sup.-3 has low vapor deposition rate and requires high gas pressure. This results in fabrication problems due to polymer formation. In addition, due to the electrode substances existing in the discharge area of the reaction chamber, thin film product is contaminated thus degrading thin film quality.
As available methods of plasma production, inductively coupled plasma deposition and capacitively coupled plasma deposition are provided. Inductively coupled plasma deposition is shown to be more efficient than capacitively coupled plasma deposition. Using inductively coupled plasma deposition, it is possible to produce plasma having a higher density such as 10.sup.11 -10.sup.12 cm.sup.-3, and for discharging to take place under low pressures such as 0.1-20 mTorr. (Refer to P. N Wainman et al., J. Vac. Sci. Technol., Al3(5), 2464, 1995.)
In the laid-open publication of Japanese patent application (No. 95-60704), there is disclosed, an inductively coupled plasma chemical vapor deposition apparatus. The above patent application, however, does not present the manufacturing method for amorphous silicon film, microcrystalline silicon film, thin silicon nitride film and thin amorphous silicon film transistors possessing superior electrical and optical matter properties. In addition, in the above disclosed apparatus, dielectric shield is made of material containing oxygen, such as quartz, and during deposition, the generated plasma causes etching of the dielectric shield, resulting in the dissociation of oxygen and other impurities from the dielectric shield which adversely effects thin film quality. Furthermore, in the above mentioned inductively coupled plasma chemical vapor deposition apparatus, gas injection holes which form a portion of gas supply unit are not located at a central region of the reaction chamber but to the side of the chamber. What results is the irregular distribution of supplied reactant gas, making difficult, the production of thin films having a large surface area. Namely, the above mentioned apparatus has a shortcoming a uniform and high density plasma within the reaction chamber is not produced.
According the ICP CVD method of the present invention, a uniform amorphous silicon is provided having superior electrical and other physical properties in areas such as photo sensitivity, electric conductivity, and optical band gap. In addition, uniform film silicon nitride with superior physical properties in areas such as electric conductivity, break down voltage, current density is provided. Thin uniform film silicon with fine crystalline grain size is also provided. Additionally, a thin film transistor having a uniform amorphous silicon film is provided with superior electrical properties in areas such as electric field effect mobility, and threshold voltage. Thus a TFT-LCD of quality can obtained according the present invention.